Cesium induced rectifications in frog myelinated fibres.

Voltage clamp experiments done on nodes of Ranvier show that external application of Cesium blocks the inward but not the outward potassium currents. Internal application of Cs ions reduces the outward K-current and the inward K-current is not affected. These results support the hypotheses that K ions cross th- K-channel after dehydration at superficial sites where competition may occur with Cs-ions.